1. Field of the Invention
The present disclosure relates to an ingot growing apparatus and a method of manufacturing an ingot.
2. Description of the Related Art
In general, a process of manufacturing a wafer for fabricating a semiconductor device may include a cutting process slicing a silicon single crystal ingot, an edge grinding process rounding an edge of the sliced wafer, a lapping process planarizing a rough surface of the wafer due to the cutting process, a cleaning process removing various contaminants including particles adhered to the surface of the wafer during the edge grinding or lapping process, a surface grinding process for securing shape and surface suitable for post-processing, and an edge polishing process for a wafer edge.
A silicon single crystal ingot may be grown through a Czochralski (CZ) method or floating zone (FZ) method. In general, a silicon single crystal ingot is grown by using the Czochralski method, which may manufacture a large diameter silicon single crystal ingot and has low processing cost.
The Czochralski method may be performed by immersing a seed crystal in a silicon melt and pulling the seed crystal at a low speed.
The seed crystal at a low temperature is in contact with the high-temperature silicon melt to thus generate a thermal shock. Shear stress may be generated in the single crystal ingot due to the thermal shock and the shear stress generates dislocations in the single crystal. The dislocations due to the thermal shock may be removed through a neck portion forming process.
A typical neck portion forming process is a technique removing dislocations by reducing shear stress through decreasing a diameter of the neck portion and increasing a crystal growth rate higher than a dislocation propagation velocity, which was suggested by Dash in the 1950s. The neck portion forming process technique disclosed so far has been performed such that a diameter of the neck portion is 5 mm or less and a crystal growth rate is 3 mm/min or more. However, since the generated shear stress increases as the diameter of the neck portion increases, the dislocation propagation velocity is more increased, and thus, it is difficult to remove dislocations in the neck portion having a diameter of 5 mm or more by simply increasing the crystal growth rate of the neck portion. A limit of the diameter able to control dislocations by a general neck portion forming process is known to be 5 mm or less.
However, it is estimated that a weight of a 450 mm crystal in the future may reach about 1 ton and it is impossible to support the heavy weight (>500 kg) of the 450 mm crystal by using the present process of forming a neck portion having a diameter of about 5 mm.
That is, since it is expected that the weight may be closed to 1 ton when a large diameter single crystal is grown in the future, there is a need for a process of forming a neck portion having a diameter able to support the heavy weight.